1. Field of the invention
The present invention relates to an irreversible circuit device and a communication device.
2. Description of the Related Art
Generally, a lumped-constant isolator (one type of irreversible circuit device) employed in mobile communication devices such as portable telephones or the like has a function of allowing a signal to pass only in the transmission direction and blocking the transmission of a signal in the reverse direction. Moreover, for recent mobile communication devices, higher reliability and lower cost have been required, due to the type of use. Accordingly, for the lumped-constant isolators as well, higher reliability and lower cost have been strongly required.
The above-described lumped-constant isolators each comprise a permanent magnet, a ferrite to which a DC magnetic field is applied, a plurality of center electrodes arranged on the ferrite, a capacitor element for matching, a resin member arranged between the permanent magnet and the matching capacitor element, a resin case which accommodates the ferrite, the center electrodes and the matching capacitor element, an upper case made of a magnetic metal which accommodates the permanent magnet, the ferrite, and the center electrodes, a lower case made of a magnetic metal, and other components known to skilled persons.
FIG. 17 is a vertical cross-sectional view of a part of a conventional isolator in which a matching capacitor element is arranged. In an isolator 200, a matching capacitor element C is soldered in a lower case 4 formed integrally with a resin case 3. A center electrode P is arranged on the top face of an input-output lead-out electrode 235 formed integrally with the resin case 3 and the matching capacitor element C. The input-output lead-out electrode 235 and the matching capacitor element C are electrically connected to the center electrode P. A resin member 230 is arranged so as to cover the input-output lead-out electrode 235, the matching capacitor element C, and the center electrode P. A convexity 231 is formed on the under face of the resin member 230 to contact the center electrode P. Reference numerals 8 and 9 designate an upper case and a permanent magnet, respectively.
In this case, the resin member 230 and the matching capacitor element C compactly sandwich the center electrode P in the thickness direction. The reason for this arrangement is to reduce the number of the assembly steps, and also, to prevent the so-called xe2x80x9ctombstonexe2x80x9d or xe2x80x9cchip-risingxe2x80x9d phenomenon, which may occur upon melting of the solder with which the matching capacitor element C is soldered, which may occur when the isolator is heated.
Referring to the structure of the isolator 200, the matching capacitor element C and the center electrode P are electrically connected to each other on the top face of the matching capacitor element C. The resin member 230 locally presses the top face of the center electrode P. Accordingly, the pressure applied when the isolator 200 is assembled, that is, when the permanent magnet 9 and the upper case 8 are mounted, is transmitted to the matching capacitor element C via the resin member 230 and the center electrode P. Thus, the pressure concentrates onto the parts of the matching capacitor element C and the center electrode P which contact each other. In some cases, the matching capacitor element C is broken.
Problems arise especially when the under face of the matching capacitor element C contacts both of the lower case 4 and the resin case. With this arrangement the matching capacitor element C is readily broken.
In response to these problems, the present invention can provide an irreversible circuit component which can easily be assembled and handled, and which has high reliability.
According to the present invention, an irreversible circuit component may comprise a permanent magnet, a ferrite to which the permanent magnet applies a DC magnetic field, plural center electrodes arranged on the ferrite, an internal component, a resin member arranged above the internal component, a metal case accommodating the permanent magnet, the ferrite, and the center electrodes, and a resin case accommodating the ferrite, the center electrodes, the internal component, and the resin member, the resin case contacting at least two contact-portions on the main face on the internal component side of the resin member.
The internal component is a resistance element, a matching capacitor element, or the like. The convexities formed on the resin case may contact the contact-portions of the resin member. The contact-portions of the resin member may comprise convexities, respectively. Moreover, the bottom of the internal component may contact the inner wall of the resin case and the surface of the metal case exposed to the inner wall of the resin case.
With the above-described structure, the pressure used when the permanent magnet and the metal case are mounted, is divided and applied to both the resin case and the internal component. Thus, the pressure applied to the internal component is reduced. This suppresses the internal component from being broken.
Preferably, the number of the at least two contact-portions is three. Thereby, the positional shifting of the ferrite (specifically, a disk-shaped ferrite) can be prevented.
Preferably, the resin member and the resin case are made of a material selected from either a liquid crystal polymer or PPS. The liquid crystal polymer and PPS have high heat resistance and low loss. Thus, the irreversible circuit component can be provided with high reliability.
In the irreversible circuit component of the present invention, the resin member may be omitted. In this case, the resin case contacts the at least two contact-portions on the main face on the internal component side of the permanent magnet.
A communication device in accordance with the present invention includes the irreversible circuit component having the above-described characteristics. Thus, the communication device can be provided with low cost and high reliability.
Other features and advantages of the present invention will become apparent from the following description of the invention which refers to the accompanying drawings.